Halomonas icarae sp. nov., a moderately halophilic bacterium isolated from beach soil in India.

A moderately halophilic, Gram-stain-negative, aerobic bacterium, strain D1-1T, belonging to the genus Halomonas, was isolated from soil sampled at Pentha beach, Odisha, India. Phylogenetic trees reconstructed based on 16S rRNA genes and multilocus sequence analysis of gyrB and rpoD genes revealed that strain D1-1T belonged to the genus Halomonas and was most closely related to Halomonas alimentaria YKJ-16T (98.1 %) followed by Halomonas ventosae Al12T (97.5 %), Halomonas sediminicola CPS11T (97.5 %), Halomonas fontilapidosi 5CRT (97.4 %) and Halomonas halodenitrificans DSM 735T (97.2 %) on the basis of 16S rRNA gene sequence similarity. Sequence identities with other species within the genus were lower than 97.0 %. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values of 22.4-30 % and 79.5-85.4 % with close relatives of H. halodenitrificans DSM 735T, H. alimentaria YKJ-16T, H. ventosae Al12T and H. fontilapidosi 5CRT were lower than the threshold recommended for species delineation (70 % and 95-96 % for dDDH and ANI, respectively). Further, strain D1-1T formed yellow-coloured colonies; cells were rod-shaped, motile with optimum growth at 30 °C (range, 4-45 °C) and 2-8 % NaCl (w/v; grew up to 24 % NaCl). The major fatty acids were summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c) and C16 : 0 and the main respiratory quinone was ubiquinone Q-9 in line with description of the genus. Based on its chemotaxonomic and phylogenetic characteristics and genome uniqueness, strain D1-1T represents a novel species in the genus Halomonas, for which we propose the name Halomonas icarae sp. nov., within the family Halomonadaceae. The type strain is D1-1T (=JCM 33602T=KACC 21317T=NAIMCC-B-2254T).

Neptunomonas marina sp. nov., isolated from seawater.

Strain HPM-16T, isolated from seawater, was characterized using a polyphasic taxonomy approach. Phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of an up-to-date bacterial core gene set (92 protein clusters) indicated that strain HPM-16T formed a phylogenetic lineage in the genus Neptunomonas. Strain HPM-16T was most closely related to Neptunomonas concharum LHW37T with 16S rRNA gene sequence similarity of 96.7%. Cells were Gram-stain negative, facultatively anaerobic, motile by means of a single polar flagellum, rod-shaped and formed white colonies. Optimal growth occurred at 30-35 °C, pH 6.5-8, and in the presence of 2-5% NaCl. C18:1ω7c and summed feature 3 (C16:1ω7c and/or C16:1ω6c) were the predominant fatty acids. The only isoprenoid quinone was Q-8. The polar lipid profile revealed the presence of phosphatidylethanolamine, phosphatidylglycerol and several uncharacterized lipids. The major polyamines were putrescine and spermidine. The draft genome was approximately 3.68 Mb in size with a G + C content of 50.5 mol%. Differential phenotypic properties, together with the phylogenetic inference, demonstrate that strain HPM-16T should be classified as a novel species of the genus Neptunomonas, for which the name Neptunomonas marina sp. nov. is presented. The type strain is HPM-16T (= BCRC 80980T = LMG 29560T = KCTC 52235T).

Endozoicomonas coralli sp. nov., isolated from the coral Acropora sp.

A novel bacterium, designated strain Acr-12T, was isolated from the coral Acropora sp. off coast of Southern Taiwan. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain Acr-12T belonged to the genus Endozoicomonas and had closest phylogenetic identity to Endozoicomonas acroporae Acr-14T (98.7%) and Endozoicomonas atrinae WP70T (97.8%). Cells of strain Acr-12T were Gram-negative, aerobic, non-motile, poly-ß-hydroxybutyrate-accumulating, rod-shaped and formed creamy white colonies. Optimal growth occurred at 30 °C, pH 7, and in the presence of 3% NaCl. Strain Acr-12T contained summed feature 3 (C16:1ω7c and/or C16:1ω6c), summed feature 8 (C18:1ω7c and/or C18:1ω6c) and C16:0 as the predominant fatty acids. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The predominant isoprenoid quinone was Q-9. The genomic DNA G + C content was 49.6 mol%. The DNA-DNA relatedness of strain Acr-12T with respect to the closest species of the genus Endozoicomonas was less than 30%. Phenotypic characteristics of the novel strain also differed from those of the closest related species of the genus Endozoicomonas. On the basis of the genotypic, chemotaxonomic, and phenotypic data, strain Acr-12T represents a novel species in the genus Endozoicomonas, for which the name Endozoicomonas coralli sp. nov. is proposed. The type strain is Acr-12T (= BCRC 80921T = KCTC 42900T).

Antimicrobial and stress responses to increased temperature and bacterial pathogen challenge in the holobiont of a reef-building coral.

Global increases in coral disease prevalence have been linked to ocean warming through changes in coral-associated bacterial communities, pathogen virulence and immune system function. However, the interactive effects of temperature and pathogens on the coral holobiont are poorly understood. Here, we assessed three compartments of the holobiont (host, Symbiodinium and bacterial community) of the coral Montipora aequituberculata challenged with the pathogen Vibrio coralliilyticus and the commensal bacterium Oceanospirillales sp. under ambient (27°C) and elevated (29.5 and 32°C) seawater temperatures. Few visual signs of bleaching and disease development were apparent in any of the treatments, but responses were detected in the holobiont compartments. V. coralliilyticus acted synergistically and negatively impacted the photochemical efficiency of Symbiodinium at 32°C, while Oceanospirillales had no significant effect on photosynthetic efficiency. The coral, however, exhibited a minor response to the bacterial challenges, with the response towards V. coralliilyticus being significantly more pronounced, and involving the prophenoloxidase-activating system and multiple immune system-related genes. Elevated seawater temperatures did not induce shifts in the coral-associated bacterial community, but caused significant gene expression modulation in both Symbiodinium and the coral host. While Symbiodinium exhibited an antiviral response and upregulated stress response genes, M. aequituberculata showed regulation of genes involved in stress and innate immune response processes, including immune and cytokine receptor signalling, the complement system, immune cell activation and phagocytosis, as well as molecular chaperones. These observations show that M. aequituberculata is capable of maintaining a stable bacterial community under elevated seawater temperatures and thereby contributes to preventing disease development.

Oceanospirillales containing the DMSP lyase DddD are key utilisers of carbon from DMSP in coastal seawater.

BACKGROUND: Ubiquitous and diverse marine microorganisms utilise the abundant organosulfur molecule dimethylsulfoniopropionate (DMSP), the main precursor of the climate-active gas dimethylsulfide (DMS), as a source of carbon, sulfur and/or signalling molecules. However, it is currently difficult to discern which microbes actively catabolise DMSP in the environment, why they do so and the pathways used. RESULTS: Here, a novel DNA-stable isotope probing (SIP) approach, where only the propionate and not the DMS moiety of DMSP was 13C-labelled, was strategically applied to identify key microorganisms actively using DMSP and also likely DMS as a carbon source, and their catabolic enzymes, in North Sea water. Metagenomic analysis of natural seawater suggested that Rhodobacterales (Roseobacter group) and SAR11 bacteria were the major microorganisms degrading DMSP via demethylation and, to a lesser extent, DddP-driven DMSP lysis pathways. However, neither Rhodobacterales and SAR11 bacteria nor their DMSP catabolic genes were prominently labelled in DNA-SIP experiments, suggesting they use DMSP as a sulfur source and/or in signalling pathways, and not primarily for carbon requirements. Instead, DNA-SIP identified gammaproteobacterial Oceanospirillales, e.g. Amphritea, and their DMSP lyase DddD as the dominant microorganisms/enzymes using DMSP as a carbon source. Supporting this, most gammaproteobacterial (with DddD) but few alphaproteobacterial seawater isolates grew on DMSP as sole carbon source and produced DMS. Furthermore, our DNA-SIP strategy also identified Methylophaga and other Piscirickettsiaceae as key bacteria likely using the DMS, generated from DMSP lysis, as a carbon source. CONCLUSIONS: This is the first study to use DNA-SIP with 13C-labelled DMSP and, in a novel way, it identifies the dominant microbes utilising DMSP and DMS as carbon sources. It highlights that whilst metagenomic analyses of marine environments can predict microorganisms/genes that degrade DMSP and DMS based on their abundance, it cannot disentangle those using these important organosulfur compounds for their carbon requirements. Note, the most abundant DMSP degraders, e.g. Rhodobacterales with DmdA, are not always the key microorganisms using DMSP for carbon and releasing DMS, which in this coastal system were Oceanospirillales containing DddD. Video abstract.

Comparative Genomics Reveals Evidence of Genome Reduction and High Extracellular Protein Degradation Potential in Kangiella.

The genus Kangiella has recently been proposed within the family Kangiellaceae, belonging to order Oceanospirillales. Here, we report the complete genome sequence of a novel strain, Kangiella profundi FT102, which is the only Kangiella species isolated from a deep sea sediment sample. Furthermore, gaps in the publicly available genome scaffold of K. aquimarina DSM 16071 (NCBI Reference Sequence: NZ_ARFE00000000.1) were also filled using polymerase chain reaction (PCR) and Sanger sequencing. A comparative genomic analysis of five Kangiella and 18 non-Kangiella strains revealed insights into their metabolic potential. It was shown that low genomic redundancy and Kangiella-lineage-specific gene loss are the key reasons behind the genome reduction in Kangiella compared to that in any other free-living Oceanospirillales strain. The occurrence of relatively diverse and more frequent extracellular protease-coding genes along with the incomplete carbohydrate metabolic pathways in the genome suggests that Kangiella has high extracellular protein degradation potential. Growth of Kangiella strains has been observed using amino acids as the only carbon and nitrogen source and tends to increase with additional tryptone. Here, we propose that extracellular protein degradation and amino acid utilization are significant and prominent features of Kangiella. Our study provides more insight into the genomic traits and proteolytic metabolic capabilities of Kangiella.

Isolation and characterization of a novel 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing plant growth promoting marine Gammaproteobacteria from crops grown in brackish environments. Proposal for Pokkaliibacter plantistimulans gen. nov., sp. nov., Balneatrichaceae fam. nov. in the order Oceanospirillales and an emended description of the genus Balneatrix.

Three novel strains namely, L1E11T, L1E4 and 228 were isolated as part of an ongoing study on 1-aminocyclopropane-1-carboxylate (ACC) deaminase expressing rhizobacteria from crops cultivated in saline affected coastal agro-ecosystems of Kerala, India. The novel strains were positive for many properties that are beneficial to plant growth including ACC deaminase (ACCd) activity that ranged from 1.87±0.27 to 2.88±0.71µmol of α-ketobutyrate/hr/mg of total protein. Presence of other traits such as biofilm formation, siderophore production, phosphate solubilisation, utilisation of root derived compounds and ability to colonise host roots indicates its plant-associated life style. In complement, the genomic data reveals gene features for higher adaptation to plant-associated environments. In-planta assays showed that L1E11T can promote and protect pokkali rice plants from 200mM NaCl stress. Phylogenetic, chemotaxonomic, phenotypic and genomic characterisation indicates that the novel strains belong to a novel genus and species of the order Oceanospirillales for which the names Pokkaliibacter gen. nov., and Pokkaliibacter plantistimulans sp. nov., are proposed with L1E11T (=DSM 28732T=MCC 2992T) as the type strain. Further, on the basis of low 16S rRNA sequence similarity, phylogenetic divergence, source of isolation and few differences in the phenotypic properties against its nearest taxon, a new family Balneatrichaceae fam. nov., is proposed to accommodate the two genera Balneatrix and Pokkaliibacter gen.nov. with Balneatrix as the type genus. An emended description of the genus Balneatrix is also presented.

The genome analysis of Oleiphilus messinensis ME102 (DSM 13489T) reveals backgrounds of its obligate alkane-devouring marine lifestyle.

Marine bacterium Oleiphilus messinensis ME102 (DSM 13489T) isolated from the sediments of the harbor of Messina (Italy) is a member of the order Oceanospirillales, class Gammaproteobacteria, representing the physiological group of marine obligate hydrocarbonoclastic bacteria (OHCB) alongside the members of the genera Alcanivorax, Oleispira, Thalassolituus, Cycloclasticus and Neptunomonas. These organisms play a crucial role in the natural environmental cleanup in marine systems. Despite having the largest genome (6.379.281bp) among OHCB, O. messinensis exhibits a very narrow substrate profile. The alkane metabolism is pre-determined by three loci encoding for two P450 family monooxygenases, one of which formed a cassette with ferredoxin and alcohol dehydrogenase encoding genes and alkane monoxygenase (AlkB) gene clustered with two genes for rubredoxins and NAD+-dependent rubredoxin reductase. Its genome contains the largest numbers of genomic islands (15) and mobile genetic elements (140), as compared with more streamlined genomes of its OHCB counterparts. Among hydrocarbon-degrading Oceanospirillales, O. messinensis encodes the largest array of proteins involved in the signal transduction for sensing and responding to the environmental stimuli (345 vs 170 in Oleispira antarctica, the bacterium with the second highest number). This must be an important trait to adapt to the conditions in marine sediments with a high physico-chemical patchiness and heterogeneity as compared to those in the water column.

Draft genome sequence of Halomonas meridiana R1t3 isolated from the surface microbiota of the Caribbean Elkhorn coral Acropora palmata.

Members of the gammaproteobacterial genus Halomonas are common in marine environments. Halomonas and other members of the Oceanospirillales have recently been identified as prominent members of the surface microbiota of reef-building corals. Halomonas meridiana strain R1t3 was isolated from the surface mucus layer of the scleractinian coral Acropora palmata in 2005 from the Florida Keys. This strain was chosen for genome sequencing to provide insight into the role of commensal heterotrophic bacteria in the coral holobiont. The draft genome consists of 290 scaffolds, totaling 3.5 Mbp in length and contains 3397 protein-coding genes.

Complete genome sequence of Kangiella koreensis type strain (SW-125).

Kangiella koreensis (Yoon et al. 2004) is the type species of the genus and is of phylogenetic interest because of the very isolated location of the genus Kangiella in the gammaproteobacterial order Oceanospirillales. K. koreensis SW-125(T) is a Gram-negative, non-motile, non-spore-forming bacterium isolated from tidal flat sediments at Daepo Beach, Yellow Sea, Korea. Here we describe the features of this organism, together with the complete genome sequence, and annotation. This is the first completed genome sequence from the genus Kangiella and only the fourth genome from the order Oceanospirillales. This 2,852,073 bp long single replicon genome with its 2647 protein-coding and 48 RNA genes is part of the Genomic Encyclopedia of Bacteria and Archaea project.